All About Olympic Water Polo - Water warriors

The game starts with a "swim-off": players line up on their respective goal lines facing the ball, which sits on a special buoy in the middle of the pool. When the referee blows the whistle, the buoy retracts and the fastest swimmer attempts to take possession of the ball and gain the offensive advantage for his or her team.

The offensive side has 30 seconds to score a goal. This is another change from Athens- until 2005, players had 35 seconds on the shot clock. If no goal is scored within this time, the ball is given to the defending side, which then launches an attack. After a goal is scored, players retreat to their own end of the pool, and the team that was scored upon brings the ball into play.

Two referees and two goal judges supervise the game. Judges evaluate whether a goal is legitimate, while referees watch for fouls.

There are two kinds of fouls in water polo, minor and major. Minor, or ordinary, fouls include hitting the ball with a clenched fist, holding the ball underwater when being tackled, pushing or blocking an opponent who does not have the ball or putting both hands on the ball simultaneously (except for the goalie). Minor fouls give the opposing team a free throw from the point of the foul.

Major, or exclusion, fouls are called for more violent or unsportsmanlike acts, such as kicking or striking an opponent, or deliberately splashing water in his or her face. They count as penalties, and the offending player is sent to the exclusion area, also known as the penalty box, for 20 seconds. A player who commits three fouls is ejected from the game. There are two penalty boxes or exclusion areas (one for each team). Each "box" is a roped off section beyond the goal line in a corner of the pool. The two boxes are positioned diagonally from each other.

Ejected players may be replaced by another player after 20 seconds, with one exception: an expulsion for brutality - a deliberate attempt to injure an opponent - means no substitution is allowed, and the team must continue minus one player.

A water polo ball is the same size as a soccer ball, but is yellow, waterproof, and weighs 400-450 grams. The women's ball is the same weight as the men's, but slightly smaller in size.

Players wear two uniforms - in case the outer suit gets ripped during the heat of battle. They also wear caps, numbered two to 13, with ear protectors to guard the head and eardrums. One team wears white caps and the other wears dark blue. Both goalkeepers wear red caps with the number one.

The game is played in a pool measuring 30 metres long by 20 metres wide, and at least two metres deep. There is a floating net at each end, three metres wide and 90 centimetres high. The length of the pool for the women's game is 25 metres.

Different coloured buoys, or cones, indicate the various lines in the playing area. White buoys mark the two goal lines and the half-distance line. Yellow buoys represent the five-metre lines. The exclusion areas are marked off as red rectangles behind each goal line.

Twelve men's teams and eight women's teams will compete in the water polo event in Beijing.

The men's teams are divided into two pools of six for a round-robin preliminary heat. The top four teams from each pool advance to the quarter-finals, and the quarter-final winners move on to the medal round. The women's teams play a full round-robin preliminary heat. The top four teams advance to the semi finals, and from there the winners advance to the gold medal game. The losing teams play for bronze.